Make demo easier to see

* README.org: Use demo.png.
* after.png:
* before.png: Delete files.
* demo.png: New file.

README.org

@@ -51,14 +51,7 @@ To keep eldoc from displaying documentation at point without enabling any minor
 
 By default, eldoc-box tries to prettify the displayed markdown documentation as shown below. If you wish to disable them, remove the prettifier functions from =eldoc-box-buffer-hook=. Report an issue if there are other things can be prettfied away.
 
-Before:
+[[./demo.png]]
-
-[[./before.png]]
-
-After:
-
-[[./after.png]]
-
 
 * Credit
 - Thanks to for [[https://github.com/joaotavora][João Távora]] for valuable contribution and explaining eldoc and eglot internals to me.